Photoflash lamp

ABSTRACT

A percussive-type photoflash lamp in which the powdered metallic combustible component of the fulminating material thereof includes hydrides of titanium and/or zirconium.

United States Patent [191 Shaffer et al.

[ PHOTOFLASH LAMP [75] Inventors: John W. Shaffer, Williamsport, Pa.;

Stephen V. Brown, Winchester, Ky.

[73] Assignee: GTE Sylvania Incorporated,

Danvers, Mass.

[22] Filed: Sept. 10, 1973 [21] Appl. No.: 395,772

[52] U.S. Cl. 431/93, 149/29 [51] int. Cl. F2lk 5/02 [58] Field ofSearch 431/93 [56] References Cited UNITED STATES PATENTS 3,724,9914/1973 'Schupp 431/93 [451 Oct. 8, 1974 5/1973 McDonough 431/93 PrimaryExaminer-Carroll B. Dority, Jr. Attorney, Agent, or Firm-Edward J.Coleman [5 7] ABSTRACT A percussive-type photoflash lamp in which thepowdered metallic combustible component of the fulminating materialthereof includes hydrides of titanium and/or zirconium.

9 Claims, 1 Drawing Figure PHOTOFLASH LAMP This invention relates to themanufacture of photoflash lamps and more particularly those of thepercussive type.

Generally speaking, a percussive-type photoflash lamp comprises anhermetically sealed, lighttransmitting envelope containing a source ofactinic light and having a primer secured thereto. More particularly,the percussivetype photoflash lamp may comprise a length of glass tubingconstricted to a tip at one end thereof and having a primer sealedtherein at the other end thereof. The length of glass tubing whichdefines the lamp envelope contains a combustible, such as shreddedzirconium foil, and a combustionsupporting gas, such as oxygen. Theprimer may comprise a metal tube and a charge of fulminating material ona wire anvil supported therein. A deflector bead is disposed on the wireanvil just above the primer tube to deflect and control the ejection ofhot particles of fulminating material therefrom. Operation of thepercussive-type photoflash lamp is initiated by an impact onto the tubeto cause deflagration of the fulminating material up through the tube toignite the combustible disposed in the lamp envelope.

The requirements that must be met by a fulminating material forpercussive flashlamps are unique and differ appreciably from those forflashlamps used heretofore in which a paste of fulminating material isheated by the passage of electric current through a wire filament untilignition occurs. Energy input to the paste usually extends'over a periodof one or more milliseconds. In contrast, energy input to thefulminating material of 'a percussive flashlamp is in the form ofasingle nearlyinstantaneous impact, the duration of which would bemeasured in microseconds. Unless ignition occurs during this singlemomentary event, the lamp has failed. Accordingly, the fulminatingmaterial for percussive flashlamps must be much more sensitive than isthe ignition paste for filament-ignited lamps.

The fulminating material for percussive flashlamps comprises four majoringredients: an oxidizer, such as sodium chlorate; a fuel, such as redphosphorus that ignites by friction or impact in the presence of theoxidizer; a binding agent, such as hydroxyethyl cellulose, to adhere thefulminating material to a specified location in the flashlamp; and acombustible metal powder, such as titanium. The metal powder is notrequired for, and does not participate in, the attainment ofmechanically initiated deflagration. It does, however, play twoimportant roles: it slows down or attenuates the reaction between thephosphorous and oxidizer, and it transports combustion from thefulminating material to the shredded metallic combustible in the lamp.

Throughout the history of percussive flashlamps there has been aconstant evolution of fulminating material performance. This has beentied principally to the nature and quantity of the powdered metalliccombustible used. The choice and relative amount of powdercd metalliccombustible has a direct effect on lamp reliability, containment, lightoutput and uniformity thereof, and output timing characteristics. It hasbeen found that powders of various metals differ appreciably in theirabilityto attenuate the phosphorous-oxidizer reaction and in theirability to ignite the shreded metallic combustible within the flashlamp.Metal powders that are relatively superior with regard to one functionmay be quite inferior with regard to the other. Sensitivity andreliability of the fulminating material both decrease as metal powdercontent increases. This is a general behavior for all kinds of metalpowder, although the relative fall-off of sensitivity and reliabilitywith increasing metal content differs from one metal to another.

Zirconium metal powder has been adopted on an industry-wide basis as thematerial of choice for use in the primer of electrically fired, filamenttype flashlamps. Zirconium was therefore used in the first fulminatingmaterials for percussive flashlamps. It was found, however, thatproblems were encountered with either reliability or light output andtiming, and that no manipulation of the formula gave completelysatisfactory results.

Additional testing showed that powdered boron gave significantattenuation of the phosphorus-oxidizer reaction and did so at a weightpercentage that did not seriously affect the impact sensitivity of themixture. Large scale testing of boron type primers showed an inherentweakness in that system the reliability of shred ignition 'by thefulminating material discharge was distinctly inferior to that providedby zirconium powder. Accordingly, compromise blends of zirconium andboron powders were next used and found to be advantageous over eitherzirconium or boron alone.

Further research showed titanium powder to be an improvement overzirconium-boron blends with respect to shred ignition reliability,especially for those lamps having a lower than average quantity offulminating material. As an added benefit, titanium powder provided asignificantly lower settling rate than zirconium in the liquidfulminating material slurry. Titaniumbased fulminating materials havenow been used in percussive flashlamps for several years; lampreliability and light output have been very good.

Recently it has been found that the light. output per unit weight ofshredded combustible burned can be increased by either chopping theshreds into short, straight lengths, or by multiply bending the formerlong shreds into small, crumpled balls or wads. Both of these changesoffer greater manufacturing economy and permit more light output from agiven size vessel. However, both short, straight lengths and crumpledwads are relatively mobile within the lamp vessel when compared to theformer long shreds. When used in percussive flashlamps especially, suchshreds are particularly susceptible to relocation and compacting by thefulminating material discharge. Burning of compacted shreds isinefficient and gives rise to both low and variable light output. Thedegree of fulminating material attenuation attainable through the use oftitanium metal powder is therefore marginal for use with the new, moreefficient types of shredded combustible.

Another development that has rendered titanium metal-based'fulminatingmaterials marginal in performance has been the sale of certain cameramodels which are highly critical to the timing characteristics of thelight output from percussive flashlamps. In particular, the so-calledrise time (which is the time it takes for the lamp to attain a specifiedintensity of output) tends to be too fast, with the associatedpossibility of photographic underexposure with those lamps that aresomewhat faster than average. In effect, part of the light output isgenerated before the camera shutter is sufficiently open to make use ofthat light.

The timing characteristics of percussive flashlamps may be slowed down(increased rise and peak times) by increasing the ratio of metal powderto phsophorus in the fulminating material. However, the degree offulminating material attenuation now required cannot be obtained by thismethod without some sacrifice in product reliability.

In view of the foregoing, one of the principal objects of this inventionis to provide an improved fulminating material for percussive flashlampsthat gives controllably delayed rise times and peak times so that thelamp light output characteristics may be better matched to the shuttertiming requirement of given camera models.

Another object is to provide attenuated fulminating materials that donot disadvantageously relocate the shredded metallic combustile withinthe flashlamp and which thereby enhance light output uniformity.

A further object is to provide a fulminating material attenuatedsufficiently to make possible elimination of the deflector bead on theanvil wires of percussive fiashlamps so as to effect a reduction inmanufacturing cost.

These and other objects, advantages and features are attained, inaccordance with the principles of this invention, by the use of metalhydride powders as the flame transport and attenuating agent in thefulminating material of percussive flashlamps. More specifically, wehave found that zirconium hydride, and titanium hydride to an even morepronounced degree, attenuate the phosphorus-chlorate reaction far morethan the pure metals do. This is known in fulminating materialformulations that are otherwise identical. By substituting titaniumhydride for titanium powder, for example, lamp peak and rise times canbe extended by a factor of two or more.

The use of metal hydride powders, and in particular titanium hydride, infulminating material for percussive flashlamps permits attainment ofdesirable slower lamp timing characteristics and at the same time allowssufficient phosphorus content to insure lamp reliability. The degree offulminating material attenuation that can be realized with thisinvention is sufficient that it makes good photometric output possiblewithout a deflector bead on the anvil of percussive flashlamps. Suchbead elimination affords a significant reduction in manufacturing costs.

Titanium hydride powder gives a greater combined degree of attenuationand reliability than does any material previously used in percussiveflashlamp fulminating materials. Zirconium hydride is somewhat lesseffcctive as an attenuating agent than titanium hydride and, because ofits higher density, settles out more rapidly from fluid suspensions.From the standpoint of settling stability in fulminating materialslurries, titanium hydride offers advantages over titanium metal becauseof its lower density (3.8 vs. 4.5).

An important alternative is the use of combinations of, for example,titanium hydride and titanium metal powders in percussive flashlampfulminating materials. Such combinations permits adjustment of lamptiming characteristics to any value lying between those for the pureseparate components. Combinations of zirconium with its hydride or withtitanium hydride may also be used. The latter combination isparticularly effective in those situations where particle settling isnot a prime consideration. Titanium hydride contributes its outstandingattenuation characteristics and zirconium its superior ability to effectshred ignition.

In the specific embodiment of the invention illustrated in theaccompanying drawing, the FIGURE is an elevational view partly insection of a percussive-type phototlash lamp. The lamp comprises alength of glass tubing defining an hermetically sealed lamp envelope 2constricted at one end to define an exhaust tip 4 and shaped to define aseal 6 about aprimer 8 at the other end thereof. THe primer 8 comprisesa metal tube 10 and a wire anvil 12 coated with a charge of fulminatingmaterial 14. A combustible such as filamentary zirconium 16 and acombustion-supporting gas such as oxygen are disposed within the lampenvelope. The wire anvil 12 is centered within the tube 10 and held inplace by a crimp 18 just above the head 20 of the anvil. Additionalmeans, such as lobes 22 on wire anvil 12, are also used to aid instabilizing and supporting it substantially coaxial within the primertube 10 and insuring clearance between the fulminating material 14 andthe inside wall of the tube 10. A refractory bead 24, fused to the wireanvil 12 just above the inner mouth of the primer tube It), eliminatesburnthroughs and functions as a deflector to deflect and control theejection of hot particles of fulminating material from the primer tube.As discussed hereinbefore, head 24 may be eliminated when usingsufficiently attenuated fulminating materials in accordance with theinvention.

By way of example, a fulminating material for percussive flashlamps inaccordance with the principles of this invention may be formulated asfollows. The anvil wire is initially dipped into an aqueous slurryhaving the following dried composition (percent by weight): 36.15percent titanium hydride powder, 2.5 micron; 36.15 percent titaniumpowder, 2.5 micron; 24.1 percent red phosphrous; 1.4 percenthydroxyethyl cellulose as a binder; 1.2 percent sodium lignin sulfonateas a chemical dispersing agent; 0.2 percent sodium Z-ethylhexyl sulfateas a wetting agent; 0.1 percent N-(3-chloroallyl) hexaminium chloride asa bactericide; and 0.7 percent magnesium oxide and sulfur (10:1 blend).The addition of a small amount of sulfur has been found to improve shelflife and impact sensitivity of red phosphorus based fulminatingmaterials, and the magnesium oxide maintains the mixture slightlyalkaline. The water content of this slurry is adjusted to give thedesired coating thickness The coating is then dried and dipped into anaqueous solution containing 25 percent by weight of dissolved sodiumchlorate. Upon drying, the resulting coating is a highly sensitive andreliable fulminating material for percussive flashlamps.

A group of percussive flashlamps of the type shown in the FIGURE andcontaining as fulminating material 14 the formulation described in thepreceding paragraph were tested against a control group of lamps whichwere identical except for employing pure titanium as the combustiblemetal powder component in the fulminating material instead of 50 percenttitanium and 50 percent titanium hydride. The average rise time for thetest lamps was 4.4 milliseconds, as compared to 3.3 milliseconds for thecontrol lamps; the average peak time of the test lamps was 9.2milliseconds, as compared to 7.6 milliseconds for the control lamps; andthe average light output in zonal lumen seconds from 0-25 millisecondswas 452 as compared to 484 for the control lamps. Hence thehydride-containing test lamps exhibited a 33 percent increase in risetime and a 21 percent average increase in peak time, while thefulminating material attenuation reduced light ouput by only 6 percent.

As previously discussed, lamp timing characteristics hafnium or boronpowder can be used in combination with the hydrides of titanium orzirconium. In addition, hafnium hydride can be used as an alternatehydride, although it is considerably more expensive.

may be adjusted by varying the combinations of tita- 5 Wh t w l i i niumhydride and titanium metal powders in the fulmi- 1. A photoflash lampcomprising: nating material. This effect is illustrated by the followanhermetically sealed, light-transmitting envelope; ing test data forpercussive lamps in which the fulminata quantity of filamentarycombustible material 1 ing material was formulated using a 3:1 ratio ofhydride r d i hi id envelope; and metal powders to phosphorus, and a 25percent so- 10 a combustionupporting gas i id v l lution of sodiumchlorate: and a primer secured to and extending from one end AverageAverage Light Output in Peak Time Rise Time Zonal Lumen Seconds TiH Ti(msecs.) (msecs.) (0-25 msecs.)

The ratio of metal hydride or metal and metal hyof said envelope and incommunication therewith, dride to red phosphorus may be varied fromabout 1:1 said primer including a charge of percussionto 8:1 on a weightbasis. The combined weight of metal sensitive fulminating materialhaving a powdered hydride, metal (if used), and red phosphorus maycommetal hydride as one of its components. prise from about 80 percentto nearly 100 percent of 2. The lamp of claim 1 wherein said metalhydride the dried composition excluding oxidizer. The oxidizer comprisestitanium hydride, zirconium hydride, or a may be incorporated in asecond operation as decombination thereof. 1 scribed. or it can bestirred into an aqueous mixture 3. The lamp of claim 2 wherein saidfulminating maprior to application. If applied by the describedimbibterial further contains powdered zirconium or powing process, theconcentration of the solution used may dered titanium, be varied fromabout 10 percent to 50 percent, or the 4. The lamp of claim 1 whereinthe principal compoupper limit of solubility for the chosen oxidizingnents of said fulminating material are a fuel, an oxiagent(s). Belowabout 10 percent, reliability is unacdizer, a powdered metal hydride anda binder. ceptable. The exact optimum percentage is a function 5, Thelamp of claim 1 wherein the principal compoof duration of immersion andthe nature of the oxidants nts f said fulminating material are redphosphorus, used. For example, mixtures of sodium chlorate with n idi abi der, nd a combustible metallic pow- Potassium Chlorate Potassium Pchlorate, or with der comprising titanium hydride, zirconium hydride orpotassium dichromate have been tested; however, a soa combinatign h f,lution of sodium chlorate alone is preferred. If the oxiv 6, Th l f l i5 h i id t lli powder dizihg agent is to be Stirred directly into theaqueous additionally contains titantium or zirconium. fulminatingmaterial slurry, it should be incorporated 40 7 Th l f l i 5 h i th r tif th d to the extent of 5 t0 5 0 Perceht y Weight of the weight of saidmetallic powder to said phosphorus is bebined other ingredients. 1 tweenabout 1 to 8.

Accordingly, although the invention has been de- 8, Th lamp f claim 5wherein said oxidizer is soscribed with respect to a specificembodiment, it will be di hl te, 1 appreciated that modifications andchanges may be 9. The lamp of claim 5 wherein the composition of made bythose skilled in the art Witho t dep r ing o said fulminating materialfurther includes relatively the spirit and scope of the invention. Forexample,'the small quantities of chemical dispersing agent, a wettingcombustible metallic powder component of the fulmiagent, a bactericide,sulfur, and magnesium oxide. nating material may also comprisecombinations of powdered titanium with zirconiumhydride. Further,

1. A photoflash lamp comprising: an hermetically sealed,light-transmitting envelope; a quantity of filamentary combustiblematerial located within said envelope; a combustion-supporting gas insaid envelope; and a primer secured to and extending from one end ofsaid envelope and in communication therewith, said primer including acharge of percussion-sensitive fulminating material having a powderedmetal hydride as one of its components.
 2. The lamp of claim 1 whereinsaid metal hydride comprises titanium hydride, zirconium hydride, or acombination thereof.
 3. The lamp of claim 2 wherein said fulminatingmaterial further contains powdered zirconium or powdered titanium. 4.The lamp of claim 1 wherein the principal components of said fulminatingmaterial are a fuel, an oxidizer, a powdered metal hydride and a binder.5. The lamp of claim 1 wherein the principal components of saidfulminating material are red phosphorus, an oxidizer, a binder, and acombustible metallic powder comprising titanium hydride, zirconiumhydride or a combination thereof.
 6. The lamp of claim 5 wherein saidmetallic powder additionally contains titantium or zirconium.
 7. Thelamp of claim 5 wherein the ratio of the dry weight of said metallicpowder to said phosphorus is between about 1 to
 8. 8. The lamp of claim5 wherein said oxidizer is sodium chlorate.
 9. The lamp of claim 5wherein the composition of said fulminating material further includesrelatively small quantities of chemical dispersing agent, a wettingagent, a bactericide, sulfur, and magnesium oxide.